1 /*	$OpenBSD: s_ccosf.c,v 1.2 2010/07/18 18:42:26 guenther Exp $	*/
2 /*
3  * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
4  *
5  * Permission to use, copy, modify, and distribute this software for any
6  * purpose with or without fee is hereby granted, provided that the above
7  * copyright notice and this permission notice appear in all copies.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16  */
17 
18 /*							ccosf()
19  *
20  *	Complex circular cosine
21  *
22  *
23  *
24  * SYNOPSIS:
25  *
26  * void ccosf();
27  * cmplxf z, w;
28  *
29  * ccosf( &z, &w );
30  *
31  *
32  *
33  * DESCRIPTION:
34  *
35  * If
36  *     z = x + iy,
37  *
38  * then
39  *
40  *     w = cos x  cosh y  -  i sin x sinh y.
41  *
42  *
43  *
44  * ACCURACY:
45  *
46  *                      Relative error:
47  * arithmetic   domain     # trials      peak         rms
48  *    IEEE      -10,+10     30000       1.8e-7       5.5e-8
49  */
50 
51 #include <complex.h>
52 #include <math.h>
53 
54 /* calculate cosh and sinh */
55 
56 static void
57 _cchshf(float xx, float *c, float *s)
58 {
59 	float x, e, ei;
60 
61 	x = xx;
62 	if(fabsf(x) <= 0.5f) {
63 		*c = coshf(x);
64 		*s = sinhf(x);
65 	}
66 	else {
67 		e = expf(x);
68 		ei = 0.5f/e;
69 		e = 0.5f * e;
70 		*s = e - ei;
71 		*c = e + ei;
72 	}
73 }
74 
75 float complex
76 ccosf(float complex z)
77 {
78 	float complex w;
79 	float ch, sh;
80 
81 	_cchshf( cimagf(z), &ch, &sh );
82 	w = cosf( crealf(z) ) * ch + ( -sinf( crealf(z) ) * sh) * I;
83 	return (w);
84 }
85